It's quite possible you have filled your quota in your inbox. When this happens you have to delete some older messages, then look for where it tells you that it's got a message saved and click there and tell it to load your message. I had this happen to me once and that was the issue. I keep my message folder much cleaner now

“You can please some of the people all of the time, you can please all of the people some of the time, but you can’t please all of the people all of the time”